As publicly known examples in relation with a skew structure of a rotor in conventional squirrel-cage induction motors, Japanese Unexamined Patent Application Publication No. H7-163108 and Japanese Unexamined Patent Application Publication No. S57-49357 disclose prior arts in which an annular short-circuit ring is provided between respective blocks and rotor conductors are short-circuited.
Although the prior arts disclosed in the Japanese Unexamined Patent Application Publication No. H7-163108 and the Japanese Unexamined Patent Application Publication No. S57-49357 are the arts in relation with a skew structure of a rotor, magnetic resistance increases at the position provided with the short-circuit ring, no-load current increases, and efficiency lowers.
An object of the present invention is to provide a squirrel-cage induction motor with high efficiency.